It is sometimes necessary to provide control signals to each of a plurality of cooperative signal processors. If all the signal processors operate synchronously, this involves providing measuring apparatus to sample parameter values from the processors, generate the control signals having values based on the relative values of the parameter values, and supply these control signals to the processing channels, all in synchronism with the processed signals. However, in cases where the data signals are not mutually synchronized, but it is still required to cooperatively control the processing of all of the data signals based on the relative values of the respective signal parameters, it is necessary that the signal parameters be sampled substantially simultaneously in all of the data signals, and that the control signals be properly valued to compensate for the asynchronous nature of the signal processors and supplied to the signal processors at appropriate times.
In an exemplary system, a plurality of video signals from respective channels, which may be television network feeds, television stations, or other video sources, are transmitted over a satellite link for broadcast to respective television receivers in consumers' homes. Each video signal may be encoded into a signal consisting of sequential groups of data, each group including data representing a fixed number of successive video pictures or frames and being designated a group of pictures (GOP). However, the video signals being supplied by these channels are not necessarily in synchronism. For example, channels carrying standard video (in the U.S.) operate at about 30 frames per second, channels carrying film images operate at 24 frames per second, and channels carrying cartoons operate at 15 frames per second. It is also possible that different channels have different numbers of pictures or frames in a GOP. Consequently, GOPs of different channels have different time durations, i.e. they are asynchronous.
In such a system, data from the different channels is combined, or multiplexed, at a head end station into a single data stream. The multiplexed data stream is then transmitted over a transmission link, such as a wire, fiber optic or radio link (such as the satellite link), to a back end station, where the channels of data from the multiplexed data stream are then separated, or demultiplexed, and supplied to the intended recipients. An exemplary satellite link includes a digital transmission path capable of transmitting 24 megabits per second (Mbps). In order to maximize efficiency and utilization of such a link, it is necessary for several video signals to share the link. For example, it may be desired to share the above satellite transmission link among at least six video signal channels.